This invention relates to magnetic heads adapted for mounting on the side of a slider.
In a typical thin film head located on the back of the slider, the pole piece is oriented perpendicularly to the direction of media travel (see FIG. 1). As shown in the figure, well defined magnetic domains 10 form in the pole tip 12, the pole having a width W and defining a track width TW. These "good" domains are capable of conducting flux by rotation of the polarization of the domains without changing the location of their wall boundaries. As shown in FIG. 2, as the width, W, of the pole tip 12 is decreased to W' to accommodate narrower track widths, TW', the domains 14 that form are "bad" in that they can conduct flux only by wall motion. That is, for the domains to change polarization, the boundary walls 16 move as shown in FIG. 3. (Media motion is perpendicular to the plane of the drawing in FIGS. 1-3 and along arrow M in FIG. 4.)
The problem with conduction of flux by wall motion is that the motion of the boundaries can be impeded by imperfections in the material. As the boundaries deform, they become temporarily stuck and only after the deformation is great enough does the boundary "snap" free of the imperfection. This sudden change in boundary location is the mechanism which generates Barkhausen noise.
To avoid decreasing the width of the pole sufficiently to result in flux conduction by wall motion, it has been suggested to mount the head on the edge of the slider rather than on the rear of the slider as is conventionally the case. By moving the pole to the side of the slider, the width of the track TW is determined by the thickness of the pole (T), not the width of the pole (W). Since pole width is not restricted, it can be made large enough for the formation of the "good" domains which do not require wall motion for conduction. FIG. 4 shows a pole 20 mounted on the side of a slider 22. Although side mounting of the transducer has been mentioned in the literature, the techniques used to create such a pole restricted the pole gap to three microns or greater. See, "A Yoke Type MR Head For High Track Density Recording", T. Maruyama et al., IEEE Conference on Magnetics, Tokyo, April, 1987 and K. Kanai et al., IEEE Trans. on Magn., MAG-11, No. 5, p. 1212, 1975. The reason that the pole gap was restricted to three microns or greater is that the gap was created by ion milling a slot and then depositing aluminum oxide within the slot. It is unlikely that this technique would be useful for creating gaps of the order of 0.5 microns as are currently used. Furthermore, the technique previously reported is incapable of making a three-pole head.